Effects of excess maternal thyroxin on the bones of rat offspring from birth to the post-weaning period

ABSTRACT Objective To evaluate, in rat offspring, bone changes induced by excess maternal thyroxin during pregnancy and lactation, and to assess the reversibility of these changes after weaning. Material and methods Twenty Wistar rats were distributed in two groups, hyperthyroid and control, that were treated daily with L-thyroxin (50 mcg/animal) and placebo, respectively. The treatment was initiated seven days before mating and continued throughout pregnancy and lactation. From every female of each of the two groups, two offspring were euthanized after birth, two at 21 days of age (weaning), and two at 42 days of age (21 days after weaning). In newborns, the length of pelvic and thoracic limbs were measured, and in the other animals, the length and width of the femur and humerus were measured. Bones were dissected, decalcified, embedded in paraffin, and analyzed histomorphometrically. Results Excess maternal thyroxin significantly reduced the length of the pelvic limb in neonates. In 21-day-old individuals, excess maternal thyroxine reduced the length and the width of the femur and the humerus. It also increased thickness of the epiphyseal plate and the percentage of trabecular bone tissue. In 42-day-old individuals, there were no significant differences between groups in relation to the parameters evaluated in the previous periods. Conclusion Excess maternal thyroxine reduced growth in suckling rats both at birth and at weaning, and it also increased the percentage of trabecular bone tissue in 21-day-old animals. These changes, however, were reversible at 42 days, i.e., 21 days after weaning. Arch Endocrinol Metab. 2016;60(2):130-7

摘要
研究目的：评估妊娠及哺乳期母体过量甲状腺素对大鼠子代骨骼的影响，并探讨断乳后此类骨骼改变的可逆性。
材料与方法：将20只Wistar大鼠（Wistar rats）分为甲亢组与对照组，两组分别每日给予L-甲状腺素（L-thyroxin，50 μg/只）与安慰剂处理。造模于交配前7天启动，贯穿整个妊娠及哺乳期。每组母鼠的子代均选取2只于出生即刻安乐死，2只于21日龄（断乳期）安乐死，2只于42日龄（断乳后21天）安乐死。对新生子代测量骨盆肢与胸肢长度；对其余受试动物测量股骨与肱骨的长度及宽度。将骨骼解剖分离后行脱钙处理、石蜡包埋，随后进行组织形态计量学分析。
结果：母体过量甲状腺素可显著降低新生大鼠的骨盆肢长度。21日龄子代中，母体过量甲状腺素可缩短股骨与肱骨的长度、减小其宽度，同时增加骨骺板厚度与骨小梁组织占比。42日龄子代中，两组间上述各评估参数均无显著差异。
结论：母体过量甲状腺素可降低乳鼠出生时及断乳时的生长水平，并可增加21日龄子代的骨小梁组织占比；但此类改变在断乳后21天（即42日龄时）可完全逆转。
《内分泌与代谢档案（Arch Endocrinol Metab）》2016年；60(2):130-7